1. Field of the Invention
The present invention relates to efficiently handling scheduling information in a mobile communication system. More particularly, the present invention relates to a method and an apparatus for handling scheduling information by a User Equipment (UE) for which a plurality of downlink carriers and uplink carriers are aggregated, in a mobile communication system.
2. Description of the Related Art
Generally, mobile communication systems have been developed for the purpose of providing communications while ensuring the mobility of users. Thanks to the rapid development of technology, these mobile communication systems have evolved to provide high-speed data communication services as well as voice communication services.
Recently, as one of the next-generation mobile communication systems, Long Term Evolution (LTE) has been standardized in the 3rd Generation Partnership Project (3GPP). LTE is technology that can implement high-speed packed-based communication having a data rate of a maximum of about 100 Mbps, which is higher than the currently available data rate, aiming at its commercialization around 2010, and its standardization has almost been completed. On the occasion of the completion of the LTE standardization, LTE-Advanced (LTE-A) systems have recently been discussed in earnest, which may further improve the data rate by combining several new technologies with the LTE communication systems. The term ‘LTE system’ as used herein may be construed to include the legacy LTE systems and the LTE-A systems. The typical one of the technologies to be newly introduced may include Carrier Aggregation (CA). In Carrier Aggregation, User Equipments (UEs) may transmit and receive data using a plurality of carriers. More specifically, a UE transmits and receives data over predefined cells (commonly, cells belonging to the same Evolved Node B (ENB)) having aggregated carriers, which is substantially the same as the UE transmitting and receiving data over a plurality of cells. Carrier aggregation includes a procedure in which an ENB transfers information about carriers to be aggregated, to UEs (this is called ‘carrier setting’), and activates the set carriers at an appropriate time in the future. The reason for using the dual procedure—carrier setting and carrier activation—is to minimize the battery consumption of UEs by driving only the transceiver for activated carriers instead of always driving transceivers for all carriers aggregated for the UEs.
Generally, in LTE systems, UEs transfer their scheduling information to an ENB, for uplink scheduling. The scheduling information may include Buffer Status Report (BSR) and Power Headroom Report (PHR).
However, in a case of a UE for which a plurality of carriers are set by the carrier aggregation, its theoretical maximum uplink data rate tends to increase in proportion to the number of set carriers. Thus, if the UE reports its buffer status in the manner of the related art, it may suffer from several inefficiencies. In addition, since the channel properties of set uplink carriers may be different depending on the frequency band of uplink carriers, reporting power headroom in the manner of the related art may cause several inefficiencies.
Therefore, a need exists for a method and an apparatus for handling scheduling information by a UE for which a plurality of downlink carriers and uplink carriers are aggregated, in a mobile communication system.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.